Executive Summary

The following report details the development and implementation of a low-cost PC based quad channel real-time / storage oscilloscope.

This project attempts to achieve the same functionality as a traditional oscilloscope, using a PIC microcontroller for data acquisition (including appropriate analogue circuitry) which transfers the data to the PC (via RS232). A Microsoft Windows based software application will then display the waveform as it would appear on a traditional CRT oscilloscope. This software application will have additional features not present on a traditional oscilloscope (e.g. printing / saving waveforms) with greater flexibly as additional features can be added as their developed without the need for new hardware.

The digital based oscilloscope should display very low frequency waveforms in real-time, but for higher frequency waveforms it is necessary to read a finite number of samples storing them into RAM. Once the memory is full (or the preset number of samples has been reached) the PIC will stop sampling and transfer the data to the PC, when ACK (acknowledgment) is received from the PC the PIC will start sampling again. This is known as a “Storage Oscilloscope”, but there are disadvantages e.g. it’s impossible to continuously monitor a waveform in real-time for more than the amount of samples that can be stored into the buffer as there would be gaps in the data. 
Main Advantages of Digital over Analogue Scopes
·    The ability to observe slow and very slow signals as a solid presentation on the screen.
·    The ability to hold or retain a signal in memory for long periods.
Core Objectives
·    Design and construct hardware required for data acquisition.
·    Design of the real-time communication protocol.
·    Design of a Windows application for displaying low-frequency waveforms in real-time.
·    Design of a simulation program.
·    Demonstrate the entire system working.
Further Development
·    Add storage functionally increasing its sampling rate to at least 20 kHz.
·    Using external ADC and external RAM, explain how it would be possible to monitor high-frequency waveforms?
·    Investigate how far this storage technique can be pushed, what are the limits?
·    Low-Cost PC Based Oscilloscope
·    PIC16F877 microcontroller for data acquisition using 4 of the built-in ADCs (4 channel scope).
·    Analogue circuitry to insure 0 to 5 V input to ADC (e.g. -100 to 100V converted to 0 to 5V, i.e. bipolar)
·    Windows application (scope.exe) for displaying waveforms.
·    Simulator program for testing graphical display, communication protocols and triggering techniques.
Possible Application
·    Demonstration oscilloscope, using data projector and laptop.
·    Large high-resolution display.
·    Windows / GUI advantage such as cut & paste into documents.
·    Low-cost (less than £50)
·    Software Upgradeable.

Final Year Project

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